Process of producing highly extensible regenerated cellulose yarn



Patented May 30, 1950 STATES PATENT OFFICE E. I. du Pont de Nemours '& Company, Wilmington, Del., a corporation of Delaware No Drawing. Original application Novemberli,

1943, Serial No. 509,280. DiVi'(l8 d and this "application November 2, 1944,=Serial"No. 561,635

A 4 Claims. I

This invention relates to improvements'in artificial "filaments and yarn. It is particularly concerned with the manufactureof regenerated cellulose yarn'havinghigh extensibilityyand is a division of copending application Serial No. 509,280, filed November 6, 1943, issued as U. S. Patent No. '2,462,927,'onMar. 1, 1949.

Filaments and yarn composed of synthetic linear polyamides, described in Carothers U. 5. Patents Nos. 2,071,253 and 2,130,948, are capable of being cold drawn, i. e. permanently elongated at ordinary temperatures and in the dry state to manytimes their original length. These polyamide yarns possess, in addition, the unique property, when being cold drawn, of "necking down during cold drawing. This fnecking down" characteristic is described in detail in Babcock U. S. Patent No. 2,289,232 and consists, as shown in detail in Figure *1 and in the specification of said Babcock patent, in thelo'caliz ing of the draw-point of the filaments to'a very narrow region which, in general, is'a portion of the length of the filament having a magnitude inthe neighborhood of the diameter of the 'filament. Although the necking down of polyamide structures is most easily understood by reference to theindividual filaments, yarns composed of several filaments possess the same phenomenon.

Regenerated cellulose filaments and yarns, produced by previously known processes, are incapable of beingelongate'd more than a limited degree, for example, about 5% to 25% of their original length when stretched in the dry'state. Furthermore, regenerated cellulose filaments produced 'byknown processes, when stretchedor permanently elongated, do not drawat a single confined point or region, or even at several confined points or regions, but the elongation occurs throughout the length ofthe filament undergoing stretching tension. 'It will be understood that in the following discussion the phenomenon of necking d0wn'will include not only the drawing at one point or regionbut will also-inclu de the drawing at two or. more points in the zone in which stress is imposed with the proviso, however, that thedrawing, as indicated in said Babcock patent, is efi'ected in very narrow regions.

:It is an object of this invention to produce artificial yarns having thelproperty of being per manently stretched to adimensiongreatly'in excess of their original length. A fmtherobject of the inventioniis concerned with the formation of regenerated cellulose filaments which can be permanently elongated to several times their original length-and which=possess the characteristic of necking down during drawing. A still further objector theinvention is concerned with the colddrawing of regenerated cellulose filaments and yarns toseveral times their original length. Another object relates to a novel aproced-ure -for making artificial syarns andfi-laments possessing the "property-0f necking down during drawing and being permanently elongated to a very large degree. An additional object pertains tothe treatment of extensible regenerated cellulose filaments whereby to greatly increase their extensibility. Other objects will appear hereinafter.

The objects ofthe invent-ion ar'e, in general, accomplished by extruding an aqueous cellulosic solution, such as viscose,through a nozzle containing one or more holes into a bath which exhibits a rapid coagulating action on the cellulose x'anthate dispersion in the viscose while at the same time possessing verylittle or no tendency under "the conditions prevailing during coagulation to convert the cellulose Xanthate to 'rege'nerated'celllilo'sa'the tension imposed on the filaments prior "to passing out of the coagulating bath being or a very low order of magnitude, pre'ferably'not inexcess of 0.01 gram per denier. The yarn is then regenerated in the relaxed state, "that is, substantiall-y free from tension. The resulting regenerated cellulose yarn is then subjected to any desired liquid treatments, such as purifying treatments and treatments with a suitable finish, and 'dried,these-steps subsequent to' regeneration also being effected while the filaments aresubstantially free from tension. The .yarn or filaments are then (treated in the relaxed state withliquid ammonia until thoroughly wetout and, after the removal of the ammonia, the yarn is then dried in the absence of tension.

The following example, which is intended to illustrate and not to restrict the invention, represents the preferred form of applying the inventiomthe 'partsproportions and-percentages being by weight:

Example] Vis'c'osecontaihing 9% cellulose and 9% caustic,

and possessing a viscosity of 224 poises, is extruded through a nozzle or spinneret having 120 holes into a bath having a rapid coagulating action but, under the conditions obtaining, exhibiting no substantial tendency to convert the cellulose xanthate to regenerated cellulose. The coagulating bath is prepared from an aqueous solution consisting of:

Per cent Moncsodium phosphate 19 Disodium phosphate 5 Sodium sulfate Water 66 sufficient phosphoric acid being added to said solution to impart to the solution a pH of 5.0. The coagulating bath is maintained at a ternperature of 75 C. The filaments pass from the spinneret through a tubular member open at both ends and submerged in the coagulating bath for a distance of '15 inches, the tubular member having an inner diameter of 18 mm. and being supported horizontally in the bath so that the only flow of bath through the tube is induced by the passage of the filaments, the bath fiow therefore being in the direction of passage of the filaments. On leaving the tubular member, the yarn is immediately removed from the bath. It is passed about a feed wheel having a peripheral speed of 816 inches per minute, with a total tension on the filaments during the travel in the bath of about 0.004 gram per denier. The yarn at the feed wheel is about 1,000 denier.

The yarn passes one or more times around the feed wheel to eliminate the danger of slippage and is allowed to drop of its own weight onto any suitable receiving surface, for example, a rectangular tray to which is imparted a predetermined oscillatory traverse which eiTects the building up, without tension, of a suitable package of yarn. The yarn package is wrapped with a cloth cover and is immersed in a regenerating bath for a period of time suificient to completely convert the cellulose xanthate to regenerated cellulose, the regenerating bath used having the same composition as the coagulating bath into which the viscose is extruded but being maintained at a boiling temperature. After having been immersed in this bath for a period of 30 minutes during which regeneration is completed, the package is then removed from the bath, is treated with a washing solution, is showered with an aqueous solution or dispersion of a suitable finish, and is dried. During all of these operations, the yarn is substantially free from tension in view of its having been collected in a completely relaxed state.

The dried yarn is then twisted and reeled to skeins, which are immersed without tension in liquid ammonia for a period of approximately 3 minutes. The yarn is then centrifuged to remove excess ammonia, and the remaining ammonia is removed by evaporation, as by drying at room temperature conditions (75 F.

The yarn produced in accordance with the above example, prior to treatment with ammonia, exhibits an X-ray diffraction pattern showing crystallinity but substantially no orientation, has a dry tenacity of about 1.0 gram per denier, a wet tenacity of 0.5 gram per denier, a dry elongation of about 100%, a wet elongation of about 120%, and can be cold drawn with a permanent elongation of about 100% of its orig- 4 inal length while exhibiting no necking down phenomenon. The cold drawn yarn shows a relatively high degree of orientation as evidenced by the X-ray difiraction pattern, which shows. distinct, oppositely opposed arcs as compared with the X-ray diffraction pattern of the yarn before cold drawing, showing clearly defined concentric rings without arcs. The yarns, after being treated with ammonia and dried, can readily be cold drawn (stretched without heat in the dry state at 60% relative humidity and 75 F.) without breaking to 3.5 times its original length (250% stretch), or, after thoroughly wetting with water, can be stretched to more than l times its original length. The ammonia treated and dried yarn prior to drawing shows substantially no orientation as evidenced by its X-ray diffraction pattern but, after cold or wet drawing to a high degree, it exhibits very marked orientation as shown in its X-ray diffraction patterns. The ammonia treated and dried yarn, particularly when it contains absorbed moisture, for example when in equilibrium with 60% relative humidity and at 75 F., exhibits a very-marked necking down during cold drawing. It also exhibits a very marked necking down during wet drawing. It also possesses a certain degree of thermoplasticity, that is, when the dry, undrawn yarn is placed in contact with a heated metal surface, the tension required to draw or permanently elongate the yarn is greatly reduced.

The viscose solution employed in the manufacture of the yarn preferably contains 9% cellulose and 9% sodium hydroxide and is ripened to a sodium chloride index of about 3.5. However, this is not essential to the invention. Good results can also be obtained by the use of a viscose solution containing 7% cellulose and 6% sodium hydroxide, or other proportions of these constituents can be used. Generally speaking, however, the higher the content of cellulose, the more pronounced the necking down characteristics after the liquid ammonia treatment. The solution is preferably prepared from slightly aged alkali cellulose, although this is not critical to the invention. The solution, prior to its extrusion into the coagulating bath, is preferably ripened to a sodium chloride index of from 3.5 to 4.5, but, here again, these values are not to be considered as limiting. The solution is preferably prepared from cotton linters cellulose of high alpha-cellulose content, and, if desired, this material can, prior to its conversion to cellulose xanthate, be etherified or esterified to a low de gree, producing, for example, glycol cellulose, cellulose glycolic acid, cellulose glycolic acid derivatives, methyl cellulose, benzyl cellulose, etc. Methyl cellulose containing, for example, 0.3 methyl group per glucose unit is illustrative of such lowly etherified or esterified materials which can be used in preparing the spinning solution.

The coagulating bath used is preferably an aqueous solution containing at least 10% dissolved phosphate, calculated for convenience as trisodium phosphate. Obviously, the phosphate is not necessarily present or even added in the form of trisodium phosphate but, in referring to said percentage, the assumption that the phosphate is trisodium phosphate facilitates the calculation of the preferred amount of phosphate ion. Alkali metal phosphates, such as the phosphates of sodium and potassium, are preferred, although other water-soluble phosphates, such as ammonium phosphate, amine phosphates, etc., can be used and the phosphates may be present arcane-.9

in forms other than the triphosphate, for example, monosodium phosphate, disodium phosphate and phosphoric acid may be used in making up the bath. Some improvement is noted Where other ingredients, such as sodium sulfate, are present in the bath together with the phosphate. The phosphate bath may contain metallic sulfates other than sodium sulfate and may also contain sulfuric acid in moderate amounts. In order to have a rapid coagulating action and slow or negative regenerating action, the pH of the coagulating bath should be maintained between 3.0 and 7.0 and preferably between 4.5 and 5.5. The broad scope of the invention contemplates the use of other types of baths, for example, slow regenerating baths and any such baths known to the art may be used, for example, ammonium sulfate-sodium sulfate baths and the like. Generally speaking, aqueous baths containing as an essential ingredient alkali metal salts of weak acids, such as phosphoric acid, sulfurous acid, lactic acid and the like, and adjusted to the proper pH by the addition of the corresponding acid or of a base, serve as excellent coagulating baths.

The coagulating bath must be1 used under such conditions that substantially no regeneration takes place during the passage of the yarn through the bath. Thus, the temperature of the bath may conveniently be in the neighborhood of 55 C. to 75 (1., although it is only necessary to use a temperature at which the bath does not exhibit any substantial regenerating effect.

The water-soluble cellulose xanthate yarn can be regenerated in any suitable type of bath. Thus, baths such as that used in the above example exert a pronounced regenerating effect at elevated temperatures, such as boilin temperature, and regeneration may be effected in the same type of bath, provided the yarn is subjected to the bath for a sufficient period of time and, where necessary, at a sufficiently elevated tem perature. Although it is preferred that the yarn be regenerated in a bath of the same composition as the coagulating bath, any suitable regenerating bath, such as dilute sulfuric acid-sodium sulfate bath (Mueller baths), may be used, or heated inert liquids such as aqueous salt solutions or glycerin may be used.

The following Table I presents examples of fast coagulating, slow regenerating spinning baths which may be used, and of the physical properties possessed by yarns produced by the use of these spinning baths:

. 0.38 0. l6 Loop, gr./den 0.95 0.55 0.67 0. 37 0. 78 0.44 Elongation:

Dry, pcrcent 114 250 131 190 115 188 Wet, percenL- 128 275 154 256 110 225 Loop, percent 100 225 96 167 100 164 Spin tension, gr./d 004 0 002 0.003 Bath travel, inches. l 15 15 It is also preferred that the same magnitude low tension of the spinning operation not be exceeded durin the subsequent regeneration, purification, drying and after-treatment of the yarn. For example, the yarn leaving the coagulating bath may be formed without tension into a cake package, as in the preferred embodiment of the invention, or the yarn may be collected free of tension in the form of overlapping loops and ringlets, as in British Patent N0. 379,880 to Topham wherein the yarn is allowed to drop freely onto a slowly moving conveyor belt which advances the yarn under showers of regenerating and purifying liquids and through a suitable drying means.

The dried yarn is preferably twisted. and wound in skein form before treatment with liquid ammonia. However, this is not necessary, provided only that the yarn is treated in a substantially tensionless state.

The above description has been generally concerned with the production of highly extensible yarn having the characteristic of necking down by the use of the specific procedure set forth, followed by two, and preferably a single treatment with liquid ammonia. It. has been found that when a single treatment with liquid ammonia does not produce the necking down property, the latter can be developed by subjecting the yarn to additional treatments with liquid ammonia. When a plurality of treatments with liquid ammonia are used, the yarn is immersed in liquid ammonia until the yarn becomes thoroughly wet out by the liquid ammonia, the ammonia removed and the yarn dried, all these steps being performed While the yarn is in a relaxed state, and this cycle of steps repeated until the necking down property is developed.

Though in the specific procedure set forth the yarn, prior to treatment with liquid ammonia, is produced by the use of fast coagulating, slow regenerating baths, particularly the phosphate bath, it has been found that the property of necking down can be developed by treatment with liquid ammonia of yarn produced without the use of fast coagulating baths having little or no regenerating action if the yarn is spun under low tension, preferably not in excess of 0.01 gram per denier, and substantially the same magnitude low tension is not exceeded during the subsequent purification, drying and after treatment of the yarn. Thus, for example, regenerated cellulose yarn spun under a tension not in excess of 0.01 gram per denier in the so-called Mueller type baths (aqueous solutions of sodium sulfate and sulfuric acid, with or without zinc sulfate and other additions) and purified and dried under the same magnitude low tension can, if subjected in the relaxed state to continued and consecutive treatments with liquid ammonia, develop the property of necking down. When a single treatment with liquid ammonia does not produce the necking down property, thelatter can be developed by subjecting the yarn to additional treatments with liquid ammonia, as previously described.

7 The following Table II includes examples of spinning baths, the physical properties possessed by yarns produced under low tensions by the use of these spinning baths, and the number of as previously described. Similarly, in treating rayon produced by standard processes as distinct from the use of fast coagulating, slow regenerating baths and where substantial tensions are used treatments with liquid ammonia required to deduring spinning or during the subsequent treatvelop the necking down property: ments up to and including drying, a plurality of Table II Spinning bath A B o D E As As As As As Spun NH; Spun NHa spun NHs Spun NH3 Spun NHS No. of NH1 treatments required to cause necking down 2 2 2 2 Denier 950 1,500 950 1,500 925 1, 425 950 1,450 958 1,520 Filaments 120 120 120 120 120 120 120 120 120 120 Tenacity:

Dry, glx/den 1.19 0. 55 1.15 0. 55 1. 13 0. 51 1. 19 0. 50 0.81 0. 43 Wet, grJden. 0. 55 0. 30 0, 55 0. 29 0. 47 0. 31 0. 53 0. 34 0. 49 0. 29 Loop, gr./den 0. 99 0.53 1. 05 0. 54 1. 03 0. 50 1.15 0. 59 0. 75 0. 41 Elongation:

Dry, per cent 75 155 52 152 50 14s 59 183 45 153 Wet, per cent 90 215 35 13s 53 190 91 247 89 255 Loop, pOI cont-.. 52 145 52 149 52 142 51 177 42 143 s in tension, gr./den 0, 003 0. 003 0. 003 0. 003 0. 003 Bath travel, inr-hes 15 7 7 7 treatments with liquid ammonia performed as spinning Composition Temper. previously described will develop the necking bath down property.

The following Table III illustrate the effect 3 M A 40% (NHMSOHDH 6D H 55 of increased tension on the extent to which the B 40% (NH1)2SO4; slightly amnioniacaln 55 yarn must be treated with liquid ammonia. to de- 0 g i gg ifig gf 2 velop the necking down property, and it also com- 0 o E 10% prism-22% No2s0i0.s% znsoi 55 pares the number of treatments with liquid ammonia necessary for regenerated cellulose yarn Where Substantial tensions were used during produced according to standard methods utilizing the coagulation in the case of fast coagulating, a b whi h possesses both p d a in slow regenerating baths, such as phosphate baths, and. rapid regenerating action, such as the either during the spinning or during the subse- Mueller type bath.

Table III Sample A B o D E F As As As T As As As Spun NH Spun NH Spun AH Spun NH Spun NR3 Spun NH No. of NH3 treatments required to cause necking down l 5 6 9 6 l0 Spin tension, gr./den 0.01 0. 06 0.10 0.17 0.20 0.83 Denier 950 1,277 903 2,050 972 1, 723 854 2,100 100 259 275 1, 05s Filaments 120 120 120 120 120 120 120 120 40 120 120 Tenacity: Dry, gr,/den 1. 05 0.57 1. 77 0,53 1.34 0.52 2. 02 0.55 1.90 0.33 3.3 0.35 Wet, gr./den 0.55 0.34 0. 93 0.42 1.05 0.54 1.55 0. 0. 0.30 1.9 0.37 Loop, gll/dell 0. 93 0.54 1.47 0.50 1. 47 0. 50 1.92 0.45 1.77 0.40 2.5 0.31 Elongation:

Dry, Percent 99 155 33 275 25 35 15 202 23 170 12 217 Wet, Per oent. 119 131 49 227 35 155 20 151 25 25s 13 197 Loop, Percent 73 145 23 151 17 37 9 45 19 155 3.1 188 Bath travel, 15555 24 30 l8 Bath temperature, C 75 U 75 75 -1 75 -1 47 47 Reference (l) (1) (2) (1) (2) (1) (2) (1) (2) Samples A, B, C and D represent yarns spun into a coagulating bath prepared from an aqueous solution of 18% N aHzPO4, 10% N 21250 and 72% Water, adjusted to a pH of 5.2 by the addition of phosphoric acid or trisodium phosphate;

Sample E represents regenerated cellulose yarn manufactured according to a standard manufacturing method by the use of a Mueller type bath; and

Sample F represents a high tenacity yarn likewise produced by spinning into a sodium sulfate-sulfuric acid-zinc sulfate bath and suitable for use in the manufacture of tire cord.

(1) signifies the yarn before the liquid ammonia treatment; (2) signifies the yarn after the number of ammonia treatments indicated in the table.

quent treatments up to and including drying, it

The above Table III also makes reference to the has been found that although the necking down 70 bath travel in inches, since the length of bath phenomenon may not be present in the yarn after a single treatment with liquid ammonia, nevertheless additional treatments with liquid a1nmonia will develop this property, the additional travel obviously has an efifect on the degree of regeneration which may take place before the yarn passes out of the spinning bath.

It has also been observed that a yarn, made by treatments with liquid ammonia being performed 75 the cellulose acetate process and made under low 9 tension conditions, which has been subjected to substantially complete saponification to produce a regenerated cellulose yarn, when subjected to a single liquid ammonia treatment for 3 minutes in the relaxed state and dried, exhibits the property of necking down and of becoming elongated on stretching several times its original length. This type of yarn, before the ammonia treatment is completely unoriented when tested by it X-ray diffraction pattern but is definitely crystalline, as shown by the shape of the concentric rings peculiar to its X-ray diffraction pattern.

The ammonia treated yarns of this invention, as stated above, possess the distinctive necking down property never before obtained in cellulose yarns. Instead of cold drawing the filaments at a relative humidity of 60% and a temperature of 75 F., they may be stretched during or after immersion for a short time in an aqueous solution of a soluble phosphate, such as mono-, dior trisodium phosphate. Drawing of the yarn in either a cold or heated stretching bath develops a high orientation along the fiber axis, but drawing of the yarn in a hot stretching bath permits a higher degree of stretching than can be obtained when the yarn is drawn in a cold stretching bath.

The following Table IV shows the physical properties of yarns prior to stretching and after stretching in a cold or hot aqueous sodium phosform-aldehyde under tension, a major portion of ammonia treated yarn, either prior or subsequent to cross-linking with formaldehyde, is substantially non-brittle. This is indeed unusual for a cellulosic yarn, since up to now all evidence points to substantial embrittlement of cellulosic yarns on cross-linking with formaldehyde; The crosslinked product posseses a higher crease angle than the uncross-linked product and is crush-resistant. So far as is known, this is the first time that a cellulosic fiber has been produced which is both crush-resistant and non-brittle and which can be used in textile operations.

Though the invention has been specifically de scribed in connection with the preferred embodiment which utilizes liquid ammonia to develop the necking down property, the invention is not restricted thereto. In general, substances which, when dissolved in water, form free hydroxyl ions may be used to develop the necking down property. Hereafter are set forth several examples of illustrative substances of the general class:

Example II In Example I, after the dried yarn is twisted and reeled to skeins, it is immersed in liquid ethylamine for a period of approximatel 3 minutes, centrifuged to remove excess ethylamine,

phate solution: and the remaining ethylamine then removed and Table IV NH; treated N Ha treated NHa treated yarn yarn yam gfjfi 32;? NH: treated stretched stretched stretched Hzent yarn cold to 217% hot to 224% hot to 291% of its original of its original of its original length length length Reference (1) (3) (4) (5) Tenacity:

Dry, gr./den 0. 9 to 1.1 0.5 to 0. 6 2.1 2. 25 2. 84 Wet, grJden 0. 4 to 0.55 0.3 to 0. 4 1.05 1.22 1.37 Loop, gr./den- 0. 85 to l. 1 0. 5 t0 0. 6 1. 80 l. 72 2. 26 Elongation:

Dry, per cent 90 to 145 175 to 285 4. 3 4. 9 5. 4 Wet, per cent 100 to 170 .190 to 300 11. 9 ll. 0 10. 4 Loop, per cent 80 to 130 170 to 280 3. 3 i 2. 7 3.8 Ratio loop to drytenacitv 0 86 0. 76 0; 80 Orientation none none high high high Reference:

(1) Yarn spun at low tension in a phosphate bath.

(2) Yam of the type referred to in (1) treated once with liquid ammonia. (3) Yarn stretched at 0. 'n bath composed of 19.1% N aHzPO4+l0% NmSO4 with pH adjusted to 5.1.

(4) Yarn stretched in bath some as (3) but at temperature of 85 (5) Yarn stretched at 100 G. in bath composed of 17.8% NaHzPO4+l0% NazSOr adjusted to pH of 4.2.

Each of the stretched yarns referred to in Table IV was obtained by passing the designated undrawn yarn through inches travel in the respective bath at the temperature set forth in the table and, while immersed in the bath, stretchin to the extent set forth in the table, removing the yarn from the bath and collecting it under the stretching tension on a bobbin and, while on the bobbin, washing it free from the bath, finishing with an emulsion of a sulfonated vegetable oil, and drying.

Though a hot aqueous solution of a soluble phosphate is the preferred stretching bath, satisfactory results are also obtained when a hot aqueous solution of potassium formate or glycerin stretching bath is used.

The yarn obtained by drawing the ammonia treated yarn in a hot stretching bath and drying under tension possesses a high elastic recovery but loses a substantial part of this elastic recovery if boiled oil, or Wet out and dried under low tension. However, if the tension-dried prodnot is cross-linked (chemically combined) with the yarn dried, all of the steps being performed without any tension on the yarn. This cycle of steps is repeated 3 times.

Erample III In Example I, after the dried yarn is twisted and reeled to skeins, it is immersed in a 30% sodium hydroxide solution for 10 minutes at 30 C., then quenched in a saturated ammonium sulfate solution, washed and dried, all of the steps being performed without any tension on the yarn. This treatment is repeated 3 times.

By the use of this invention, it has become possible to produce cellulosic yarns having many of the properties of polyamide yarns, particularly the ability to be stretched many times their original length and the localizin of the drawpoint, i. e. necking down. The imparting of these new properties to cellulosic yarns widens the field of application of yarns of this general type, especially where it is required that the yarn possess a high Work factor, i. e. the ability to elongate greatly under conditions of stress.

Although the advantages of the invention are more apparent in the preparation of yarns comprising a number of filaments, it is obvious that the same advantages follow when the invention is applied to the preparation and treatment of monofils.

Since it is obvious that many changes and modifications can be made in the above-described details without departing from the nature and spirit of the invention, it is to be understood that the invention is not to be limited thereto except as set forth in the appended claims.

I claim:

1. The process of producing a yarn of high extensibility measuring at least 100% and having the property of necking down during drawing, which comprises thoroughly wetting a dried regenerated cellulose yarn having high extensibility and whose X-ray diffraction pattern shows crystallinity and substantially no orientation with liq- 1 uid ammonia, and removing the ammonia to dry the yarn, the wetting with ammonia and the ammonia removal steps being performed a plurality of times, while the yarn is in a relaxed state, until said orientation and said crystallinity are eliminated and the property of necking down is developed and the extensibility of the yarn increased.

2. The process which comprises thoroughly wetting a dried regenerated cellulose yarn having high extensibility and whose X-ray difiraction pattern shows crystallinity and substantially no orientation with liquid ammonia, removing said ammonia from the filaments, the wetting with ammonia and the ammonia removal steps being performed while the yarn is in the relaxed state whereby said orientation and said crystallinity are eliminated and the property of necking down is developed and the extensibility of the yarn increased, said extensibility measuring at least 100%, and stretching said yarn to greatly increase its length.

3. The process which comprises thoroughly wetting a dried regenerated cellulose yarn having high extensibility and whose X-ray diffraction pattern shows crystallinity and substantially no orientation with liquid ammonia, removing said, ammonia from the filaments, the wetting with ammonia and the ammonia removal steps being performed while the yarn is in the relaxed state whereby said orientation and said crystallinity are eliminated and the property of necking down is developed and the extensibility of the yarn increased, said extensibility measuring at least 100%, and stretching said yarn in the presence of a hot liquid to greatly increase its length.

4. The process which comprises thoroughly wetting a dried regenerated cellulose yarn having high extensibility and whose X-ray diffraction pattern shows crystallinity and substantially no orientation with liquid ammonia, removing said ammonia from the filaments, the wetting with ammonia and the ammonia removal steps bein performed while the yarn is in the relaxed state whereby said orientation and said crystallinity are eliminated and the property of necking down is developed and the extensibility of the yarn increased, said extensibility measuring at least 100%, and stretching said yarn in the presence of a hot aqueous solution of a phosphate to greatly increase its length.

RUDOLPH WOODELL.

REFERENGES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,200,774 Steimmig Oct. 10, 1916 1,724,670 Lilienfeld Aug. 13, 1929 1,989,098 Lilienfeld Jan. 29, 1935 1,998,551 Mahn Apr. 23, 1935 2,249,745 Charch et a1 July 22, 1941 2,297,746 Charch et a1 Oct. 6, 1942 2,301,003 Zetsche et al Nov. 3, 1942 2,327,516 Fink et a1 Aug. 24, 1943 FOREIGN PATENTS Number Country Date 279,137 Great Britain Oct. 18, 1927 335,176 Great Britain Sept. 17, 1930 488,095 Great Britain June 29, 1938 546,673 Great Britain July 24, 1942 

1. THE PROCESS OF PRODUCING A YARN OF HIGH EXTENSIBILITY MEASURING AT LEAST 100% AND HAVING THE PROPERTY OF NECKING DOWN DURING DRAWING, WHICH COMPRISES THROUGHLY WETTING A DRIED REGENERAGED CELLULOSE YARN HAVING HIGH EXTENSIBILITY AND WHOSE X-RAY DIFFRACTION PATTERN SHOWS CRYSTALINITY AND SUBSTANTIALLY NO ORIENTATION WITH LIQUID AMMONIA, AND REMOVING THE AMMONIA TO DRY THE YARN, THE WETTING WITH AMMONIA AND THE AMMONIA REMOVAL STEPS BEING PERFORMED A PLURALITY OF TIMES, WHILE THE YARN IS IN A RELAXED STATE, UNTIL SAID ORIENTATION AND SAID CRYSTALLINITY ARE ELIMINATED AND THE PROPERTY OF NECKING DOWN IS DEVELOPED AND THE EXTENSIBILITY OF THE YARN INCREASED. 